Having a photorealistic earth in the background of an animation
First, know that the physical phenomenons that come in place in the Earth's atmosphere (including those that come at the edge between day and night) are rather complicated. So if you want to do realistic "GRAVITY-style" CGI, you have a lot of work, certainly much more than what you did with your satellite. 
If for some reason you don't want to simply use a single high-res photo of a low orbit view as the background and want to make it with as much CG as possible here's what you can start with :


the Earth's texture has to be focused on a particular area, or else you will waste a ton of memory or simply have a pixelated result.
I suggest using OpenTopography to generate color and heightmap, because at this zoom level you should also see the displacement of the mountains.
for the clouds layer I don't know of a better way than using an image like this, although it will not give very realistic results, since again at this zoom level you should see them in 3D and very sharp. You could even see the projection of their shadow in the atmosphere itself, which if you want to do that using volume scattering will explode your render time.
for the day-night shift, you'd have to simulate the red twilight in some way. 
Unfortunately I don't think there's any tutorial on that but if you know your nodes you can get something close.